This invention relates to injectors for administering medication with a syringe and a hypodermic needle or cannula.
Many different types of syringes and hypodermic needles have been used for administering various types of medications. U.S. Pat. No. 3,378,008 to Ogle (1968) discloses a hypodermic syringe and vial prefilled with an injectable liquid, such as medication to be administered to a patient. Although that type of syringe has been successful, it has the disadvantage of presenting an exposed needle, which can cause an accidental injury, infection, or exposure to dangerous and toxic medication.
U.S. Pat. No. Re 33,617 to Ogle, II (1991) discloses injection apparatus which includes a protective sheath disposed around the sharp end of a hypodermic needle to prevent accidental sticking. This device has been widely accepted by the industry. However, it does not have any kind of a lockout feature to prevent medication from being administered inadvertently through an improper site, which might subject a patient to medication at a rate in too high a concentration for the safety of the patient. For example, some medication, such as morphine sulfate, is sold as a fairly concentrated medication, e.g., 50 mg of morphine sulfate per milliliter of solution, and must therefore be diluted, say, in an intravenous bag or container of saline solution, or mounted in a pump which limits delivery of the medication to safe increments over a safe period of time.
Because of the dangerous nature of certain drugs or medications, they have been sold in packages of relatively low volume to minimize the possibility of overdosing. However, this is inconvenient because it requires a large number of individual containers and adds to the work of medical personnel in administering the medication to patients.